The present invention relates to a needle coated on its surface with polyorganosiloxane.
It is a conventional technique to treat a metal surface with a silicone compound to reduce piercing resistance. For example, Japanese Patent Publication Sho (Tokko-sho) 46-3627 discloses a metal cutting blade having on its surface an adhesive coating material which comprises a siloxane unit having an amino group and an organosiloxane unit. When the adhesive coating material is applied to a needle, the coating material makes it possible to reduce piercing resistance. However, it is a problem that if the needle is used repeatedly, the coating is peeled off because curing of the adhesive material is not sufficient. Such repetition occurs when a liquid medicine is stored in a vial. That is, the needle is used to pierce a rubber lid of a vial to introduce the liquid medicine into a syringe tube, and then the liquid medicine is injected into a human body through the needle. It is also a problem that gamma ray irradiation cannot be applied for sterilization to the needle having the adhesive coating because the piercing resistance of the needle is increased by gamma ray irradiation.
Meanwhile, Japanese Patent Publication Sho (Tokko-sho) 61-35870 discloses a needle coated with a material prepared by a reaction between a reaction product of a silane containing an amino group and a silane containing an epoxy group and a polydiorganosiloxane having silanol group at a terminal end, and cured at room temperature or by heating at 100.about.150.degree. C. The coating has excellent curing characteristics because it contains silane having an epoxy group. However, piercing resistance of the needle cannot be reduced sufficiently to reduce a patient's pain because the coating is too hard.
Further, Japanese Laid-open Hei (Tokai-hei) 7-178159 discloses coating a needle with a coating agent comprising a specific polyorganosiloxane having amino group and a specific polyorganosiloxane, and treating the surface by a curing method including gamma-ray irradiation. Although the piercing resistance of the needle is reduced when the coating is cured by gamma-ray irradiation, when the coating is cured by methods other than gamma-ray irradiation, the resistance is not necessarily reduced. Therefore, a sterilization method is limited to gamma-ray irradiation.